rosdep update read operation time out 不用翻墙的解决方法

在安装ros时，运行 rosdeo update，因为网络原因，一直出现超时错误：

rosdep update
reading in sources list data from /etc/ros/rosdep/sources.list.d
Hit https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/osx-homebrew.yaml
ERROR: error loading sources list:
The read operation timed out

原因不想考究了，大家应该都知道。下面详细说下解决方法：

1. git clone https://github.com/ros/rosdistro.git 到本地，记住这个rosdistro目录的路径，例如我git clone 到了路径 /home/robot/rosdistro/

2. 查找 文件/usr/lib/python2/dist-packages/rosdep2/rep3.py 中的raw.githubusercontent.com，将 https://raw.githubusercontent.com/ros/rosdistro/master 替换成 file://+第1步中的路径，比如我的是：将 原来文件中的 REP3_TARGETS_URL = 'https://raw.githubusercontent.com/ros/rosdistro/master/releases/targets.yaml' 替换成 REP3_TARGETS_URL = 'file:///home/robot/rosdistro/releases/targets.yaml'

3. 同第2步，查找文件/usr/lib/python2/dist-packages/rosdistro/init.py中的raw.githubusercontent.com，将 https://raw.githubusercontent.com/ros/rosdistro/master 替换成 file://+第1步中的路径，比如：将 原来文件中的 DEFAULT_INDEX_URL = 'https://raw.githubusercontent.com/ros/rosdistro/master/index-v4.yaml'替换成 DEFAULT_INDEX_URL = 'file:///home/robot/rosdistro/index-v4.yaml'

4. sudo rosdep init 重新生成/etc/ros/rosdep/sources.list.d/20-default.list，将该文件中的所有https://raw.githubusercontent.com/ros/rosdistro/master 也替换成 file://+第1步中的路径，比如我修改后的文件：

# os-specific listings first

yaml file:///home/robot/rosdistro/rosdep/osx-homebrew.yaml osx

# generic

yaml file:///home/robot/rosdistro/rosdep/base.yaml
yaml file:///home/robot/rosdistro/rosdep/python.yaml
yaml file:///home/robot/rosdistro/rosdep/ruby.yaml
gbpdistro file:///home/robot/rosdistro/releases/fuerte.yaml fuerte

# newer distributions (Groovy, Hydro, ...) must not be listed anymore, they are being fetched from the rosdistro index.yaml instead

5、然后就可以顺畅的rosdep update了。